High energy liquid oxidizer comprising cif5 and of2



Feb. 17, 1970 T. A. WHATLEY 3,496,038

HIGH ENERGY LIQUID OXIDIZER COMPRISING ClF AND OF Filed Aug. 26, 1965 VAPOR PRESSURE 0F MIXTURE AT-78.9C

45OFTTTTT 5 2 l l IDEAL VAPOR PRESSURE THOMAS A. WHATLEY I'NVENTOR.

KATTORNEY 3,496,038 HIGH ENERGY LIQUID OXIDIZER COMPRISING ClF AND P Thomas A. Whatley, Santa Clara, Calif., assignor to United Aircraft Corporation, East Hartford, 'Conn., a corporation of Delaware Filed Aug. 26, 1965, Ser. No. 483,391 Int. Cl. C09k 3/00; C06b 15/00 US. Cl. 149-1 2 Claims This invention relates to a novel composition of matter suitable for use as an oxidizer in rocket propulsion systems, and, more particularly, relates to solutions of oxygen difiuoride (OB) and chlorine pentafluoride (C1F 0P is presently recognized as one of the most desirable high energy liquid oxidizers, both from the point of view of specific impulse, as .well as storing and handling properties. However, since 0P is not hypergolic at low temperatures with most conventional fuels, an auxiliary ignition system must be used when 0P is an oxidizer, thereby increasing the weight of the rocket system. 0P also has a fairly high vapor pressure which limits its use to some extent in deep space missions requiring space storable oxidizers because it has a low but finite boil-off rate. Because of this undesirable characteristic, tetrafiuorohydrazine (N F has been considered as a suitable oxidizer for deep space missions, but this oxidizer has a history of instability. In attempting to improve the characteristics of OR, several additives have been considered. The interhalogen chlorine monofluoride (ClF) theoretically could be expected to be miscible with 0P because of the similarities in molecular weight, boiling points, and the lack of intermolecular forces between the like molecules. This has, in fact, been experimentally vertified. However, when attempts to increase the fluorine content of the additive have been made, for example, with chlorine trifluoride (ClF theoretical analysis of the system indicates that ClF and OF would not be expected to exhibit much solubility or miscibility because of the dissimilarities in their molecular weights and their boiling points (boiling point of 0P is 145 C. and the boiling point of ClF is +11 C.). Experimentally, there was no apparent solubility of C11 in liquid 0P Because of the even greater differences in molecular 'weight between ClF and 0P it was expected that even less solubility or miscibility of OF and ClF would be observed. However, contrary to the theoretical prediction, it was discovered that ClF has some solubility in 0E even at OF temperatures, and, further, that is is possible to form completely miscible systems of 0P and C11 This unexpected discovery now makes it possible for a designer to combine the desirable features of both OE, and ClF Since OF is presently considered one of the best space storable oxidizers, and ClF is considered one of the best earth storable oxidizers, the ability to obtain miscible solutions of both compounds greatly increases the designers flexibility in choice of systems.

It is, accordingly, a primary object of this invention to provide a novel composition of matter, comprising a miscible system of 0P and ClF It is another object of this invention to provide a solution of ClF and 0P It is a further object of this invention to enhance the hypergolicity of OR.

It is another object of this invention to provide a means for enhancing the space storabiliy of 0P These and other objects of the invention will be readily 3,496,038 Patented Feb. 17, 1970 apparent from the following description with reference to the accompanying drawing which is a vapor pressure curve of the OF /CIF system.

The curve of the figure was prepared by charging preselected mixtures of 0P and ClF into a suitably pressurized container maintained at Dry Ice-acetone temperature of 78.5 C., and at a pressure sufficient to keep the materials in liquid form; and the equilibrium vapor pressures of the resultant mixtures were determined by conventional means. A smooth curve without a plateau is obtained as indicated in the figure, and this is conclusive evidence that the two compounds are miscible in all proportions at this temperature. Further, since significant vapor pressure lowering results, this vapor pressure lowering has the effect of increasing the upper temperature storability of 0P Since presently estimated equilibrium conditions for deep space applications is between C. and -50 C., the formation of a miscible solution of OF and ClF at or near these temperature ranges has great application therein. For example, the addition of approximately 10% of ClF to the OF produces a marked drop in the vapor pressure of the system, and, therefore, would greatly enhance the space storability of the oxidizer. Such a 10% solution of ClF in 0P also will permit a hypergolic reaction with such conventional fuels as hydrazine or the light hydrocarbons, for example, thereby eliminating the need for a separate ignition system in deep space applications. The great advantage of the miscible systems of ClF and 0P really lies in the high degree of flexibility that the designer now possesses. For example, if it is desired merely to enhance the hypergolicity of the OB, only the amount of C11 necessary to provide hypergolicity with the specific fuel material need be added to the system; on the other hand, if it is desired to decrease the vapor pressure of the system, then the amount of ClF necessary to bring the vapor pressure down to the desired level can be added. In between these two parametric extremes, any mixture of 0P and ClF can be utilized to meet the particular design requirements of the system. It is noted that the solution of minute amounts of ClF in 0P will enhance the hypergolicity of the mixture, and the minimum amount of ClF necessary to insure hypergolicity depends, of course, on the particular fuel material being used. These values can be readily determined and are not critical to this invention. The im portant feature is that composition be in the form of a solution so that there is no phase separation of the 0P and ClF To establish solubility of C11 in 0P at liquid 0P temperatures, ClF was condensed in a glass tube and then frozen therein. OR, was then condensed onto the solid ClF in amounts of approximately 84% by volume OF 16% ClF The mixture was agitated and gradually warmed. The interface between the ClF and 0P was observed to recede, clearly, indicating that some solubility of ClF in 0P was present even at temperatures of about C.

Although ClF is slightly soluble in 0P at liquid 0P temperatures of approximately 145 C., the system at that temperature does not appear to be completely miscible. Therefore, there is an intermediate temperature between the experimental temperature of 78.5 C. used herein and 145 C., below which the systems are not completely miscible. However, at temperatures above 78.5 C., the systems will be completely miscible up to the critical temperature of the system above which the system can no longer remain in liquid form. Snice the 2. A novel composition of matter consisting essentially critical temperature of 0P is about 58 C., this misof aliquid phase solution of ClF and OF cibility of C11 and 0P exists over a substantial temperature range. While this invention has been described with References Cited respect to specific embodiments theerof, this description is 5 Stacey et 1 Advances in Fluorine Chemistry, vol 4 for purpose of illustration only, and should not be con- 1965 213) 4 and 240. stiued as limiting the invention. The invention is limited only by the following claims wherein: LELAND A. SEBASTIAN, Primary Examiner I c aim:

1. A novel composition of matter comprising a liquid 10 US. Cl. X.R.

phase solution of ClF and OF 252-186 

